This invention relates, in general, to devices for testing electronic circuits, and more particularly to wafer type probes for testing high frequency electronic circuits on semiconductive or dielectric substrates.
Wafer probes provide interim electrical contact between testing equipment and the contact structures (bonding pads) of small integrated circuit (IC) devices formed on semiconductor substrates or wafers. By using wafers probes, manufacturer's obtain electrical data from the IC devices prior to separating, bonding, and packaging each IC device on the wafer. This data permits a manufacturer to monitor the manufacturing process, to respond to processing problems, and to make process adjustments before incurring additional manufacturing costs.
A major problem with most existing high frequency (greater than 100 mega-hertz) wafer probes is that they are bulky and very expensive. This has prevented their widespread use in a manufacturing environment. In particular, most existing high frequency wafer probes, such as that shown in U.S. Pat. No. 4,697,143 issued to Lockwood et al., are formed on large mounting blocks that take up significant room on a wafer tester. Because of their size, these wafer probes make it difficult to include several high frequency wafer probes alone or together with DC probes on a tester in order to probe wafers having a high density of bonding pads.
Also, most existing high frequency wafer probes use transmission line assemblies or rigid insulative substrates having conductive transmission lines formed on them to make contact to the IC devices. Because the substrates are rigid, the terminations or tips of the individual transmission lines are fixed or inflexible, making it difficult to probe bonding pads having variable height. In addition, these wafer probes can cost several thousands of dollars. This high cost makes it prohibitive to manufacture different IC device bonding pad layouts because a manufacturer would have to purchase a different high frequency probe for each bonding pad layout. Furthermore, most existing blade style high frequency wafer probes use a microstripline design, which in some application provides inadequate signal isolation.
Thus, there exists a need for a high frequency wafer probe apparatus that permits the use of a plurality of high frequency wafer probes within the wafer probe apparatus, that has probe tips that are less sensitive to variable bonding pad height, and that is cost effective. In addition, there exists a need for a cost effective high frequency stripline blade probe.